1. Field of the Invention
This invention relates to a gas turbine engine, intended for aircraft propulsion, of the type comprising a gas generator which feeds two overlapped counterrotating slow-power turbines.
2. Discussion of the Background
FR-A-2 535 394 describes a gas turbine engine of this type in which the power turbines are placed downstream from the gas generator and are driven directly by the hot gases exiting said generator. Said turbines drive directly, without a reduction gear, either two stages of counterrotating propellers or two stages of ducted fans by which the propulsion is assured. Two mounting solutions are proposed. One provides for placing the propellers or the fans behind the engine, which presents drawbacks and difficulties during mounting under the wings of an aircraft. The other provides for placing them in front of the engine, which, for driving, calls for connection shafts of great length whose installation also comprises drawbacks.
FR-A-2 560 642 describes a gas turbine engine of the same type in which a counterrotating supercharging compressor is associated with counterrotating front fans. A device for adjusting the pitch of the blades of a fan stage is added, making it possible to obtain reversal of the flow.
FR-A-2 606 081 in the name of the applicant describes another solution for the same type of engine comprising a gas generator in which the gases circulate from the rear to the front relative to the direction of movement of the aircraft and feed, after a reversal of direction, two counterrotating power turbines directly driving two stages of counterrotating propellers. The gas generator is fed by an air intake duct consisting of a multiplicity of ducts placed circumferentially around the cowl of the engine, and the exhaust of gases at the outlet of the power turbines is performed by a multiplicity of ducts interposed between the intake ducts.
If this solution makes it possible to produce a traction-type counterrotating fan engine with a cantilever in front of the aircraft wing which is smaller than the prior solutions made possible, the fact nonetheless remains that the production of the air intake duct and the flow outlets downstream from the slow turbines are fairly complicated to achieve.